SAN ANTONIO (AP) — Texas Rep. Joaquin Castro says he won’t run for the U.S. Senate in 2018 after spending months considering a run against Republican Sen. Ted Cruz.

The Democrat’s announcement Monday helps clear the Democratic primary field for his fellow Texas congressman, Beto O’Rourke, who has already launched a Senate campaign. Cruz is coming off a failed run for president and will be seeking re-election for the first time.

The 42-year-old Castro is a rising Democratic star along with his twin brother, Julian, who was the nation’s housing secretary under President Barack Obama.

Joaquin Castro says he decided that focusing on his duties in the U.S. House Foreign Affairs and Intelligence Committee is what’s best now.